The trend to higher density electrical connectors has witnessed centerline spacings of in excess of 0.150 inches reduced to spacings half of that, then one-third of that and in many instances, one-sixth; or, on the order of 0.025 inches in certain mother board constructions. By this is meant that the conductive paths or pads on the surfaces of a board are spaced on centers on the order of 0.025 inches, typically in one or several rows on the edges of the board or in certain instances, in rows well within the periphery of the board. The trend to smaller centerline spacings is driven by a variety of technical advances, including the ability to build very complex electronic integrated circuits, indeed whole computer functions in a single integrated circuit that require, in certain instances, hundreds of conductive paths serving as inputs and outputs of the device to related components. A further technical reason for the trend has been the use of higher speed signals which function better with shorter path lengths but in turn require additional parallel grounding paths to maintain desirable impedances for signal transfer.
A significant problem associated with these trends has to do with the difficulty of manufacturing very small, fine electrical contacts and terminals, the difficulty of designing dies and stamping and forming such contacts along with the difficulty of molding housings having cavities small enough to accommodate such contacts on close centers.
U.S. Pat. No. 4,869,672 deals with a dual purpose card edge connector that has contact elements disposed in an insulating housing alternately located at two different levels which effectively doubles the number of circuit traces that can be accommodated in a given connector length. The connector of the patent is intended to accommodate daughter boards having contact paths on different centers but nevertheless teaches a certain construction which facilitates increasing the capacity of a connector to connect the paths of a daughter board to a mother board. In this patent, the contacts engaging the daughter board are arranged in two rows engaging each side of a daughter board and the contacts extend to be soldered into a mother board in two rows for each side of the daughter board in order to achieve the intended purpose of the connector. The connector construction of the aforementioned patent allows for an interconnection between daughter and mother boards of 0.025 inches for each linear inch of board engagement but the invention concept relies upon utilizing two rows for each side of a daughter board and four rows of contacts for the mother board.
The present invention, on the other hand, seeks to provide an interconnection between daughter and mother board essentially half of the foregoing with contact pads in a single row on a mother board being 0.025 inches apart.